Do salmon lice, Lepeophtheirus salmonis, have a role in the epidemiology of amoebic gill disease caused by Neoparamoeba perurans?

Amoebic gill disease (AGD) is an acute to chronic proliferative condition of farmed Atlantic salmon caused by Neoparamoeba perurans (see Young, Crosbie, Adams, Nowak & Morrison 2007; Young, Dykova ´, Snekvik, Nowak & Morrison 2008a).AGD and N. perurans have been reported in most salmon-producing countries except Canada.In western North America, AGD occurs in Washington State but not in the adjacent British Columbia (B.C.).Despite the ubiquitous distribution of the disease and its causative agent, reservoir populations of the amoeba and the mechanism(s) of transmission to and among farmed fish have not been elucidated.The purpose of this study was to conduct a preliminary survey for reservoirs of N. perurans at or adjacent to salmon populations suspected to be affected with AGD.Forty Atlantic salmon, Salmo salar, were sampled in September 2008 -twenty from a farm in Puget Sound, Washington State that historically has been affected by AGD (Kent, Sawyer & Hedrick 1988;Douglas-Helders, Saksida, Raverty & Nowak 2001; Young, Dykova ´, Nowak & Morrison 2008b) and twenty from a farm near Campbell River on